In my U.S. Pat. Nos. 4,909,111 and 5,090,283 I describe a saw table that adapts normally portable circular saws for use in cutting with the heel of the saw blade. This table is used primarily for cutting wooden trim lumber but is also used in the trade for cutting siding for houses, which siding, particularly where made of poly vinyl chloride, tends to shatter when cut with a forward part of the saw blade.
The width of commercial siding does not normally exceed 30 cm. (12 in.). Where the siding must be cut to conform to a gable end of a house, for example, the angle of cut required may be quite small eg. 14.degree. , corresponding to a roof pitch of 3 in 12. The length of cut at this angle, assuming the width of the siding to be 30 cm. is approximately 120 cm. (48 in.), and considering that the saw blade is required to clear both edges of the siding when making the cut, the length of travel of the saw will be approximately 150 cm. (60 in.). While a saw table constructed in accordance with my above patents has been made sufficiently large to accommodate this length of cut, this has some disadvantages.
In U.S. Pat. No. 3,872,755, a saw table is described in which a long guide bar assembly is mounted from the cutting table. The guide bar assembly comprises long guide bars which are mounted transversely above the table deck at their ends on a beam which is fastened to the underside of the table with a vertical pivot bolt. In order to stabilize the beam relative to the table, the pivot bolt is placed towards the middle of the table. The cutting fence of the table is generally located adjacent the back edge of the table; accordingly, when the guide bar assembly is rotated, the point of intersection of the cutting path of the blade of the saw with the fence line of the table moves. This requires that a measuring tape zeroed at the point of intersection be adjusted each time the angle of rotation of the guide bar assembly is changed relative to the table, in order to facilitate the correct positioning of the work to be cut on the table. If the cut is to be made with the heel of the blade by pulling the saw backwards, the guard of the saw must be raised to expose the saw blade. When the narrow guide bar assembly is rotated so as to be in a position at or near right angles to the cutting path of the saw, the saw can be moved past the table for a significant distance. If the guard were retracted to cut in the backward pulling mode, the exposed blade would create a significant operator hazard.
In another commercial adjustable table design, the top of the beam is flush with the cutting surface and is flush with the deck, and helps to support the work to be cut when the table is generally at right angles to the cutting path of the saw. The table deck is thus bisected by the beam and consists of two sliding sections. As the beam is moved to acute cutting angles, these deck sections must spread apart so that increasingly wide gaps are created between the deck surfaces and the cutting beam surface so that support for the workpiece is not continuous. And again, measuring tapes installed in fence pieces or decks must be rezeroed after each change of angle.